Is good that there was an export to the UK. Maybe as early as the 1930’s but took off when ported by GI’s lugging their vinyl records with them when stationed in the UK in WWII and afterwards. The English added more electric guitar work so there is a sort of a unique “British Blues” sound.
There is also a strong emphasis on improvisation in the Blues that derives from Scat singing (think Louie Armstrong). The variations that derive from American Blues probably appeals to many here even if they do not realize the roots are more Americana than even Apple Pie!
The following may appeal only to junior musicologists but if you are curious about what American music and how it came into being this is sorta of interesting and really well done: